The present invention relates to laminate structural panels and, more specifically, to light-weight laminates having desirable structural characteristics.
Sheet steel is used extensively to form panels. The required structural characteristics, such as stiffness, vary depending upon the specific application. When higher stiffness values are required, the steel thickness is typically increased. Increasing sheet steel thickness, however, produces a panel which is not only heavier, but also more expensive.
A number of approaches have been taken in the past to provide improved structural characteristics of panels, without substantially increasing weight or materials cost. For example, composites of steel sheets having a solid polymer core have been used in applications where sound deadening and vibration dampers are required. The specific stiffness of polymer core products, however, is less than desirable.
In copending U.S. patent application Ser. No. 08/947,030, filed Oct. 8, 1997, entitled STRUCTURAL PANEL WITH KRAFT PAPER CORE BETWEEN METAL SKINS, the entire disclosure of which is incorporated herein by reference, structural panels are disclosed which are laminate structures having metals skins separated by and bonded to an intervening layer of paper. The laminates described therein have high specific stiffness.
In copending U.S. patent application Ser. No. 09/342,690, filed Jun. 29, 1999, entitled CARGO VEHICLE WALL, the entire disclosure of which is incorporated by reference, truck trailers having walls formed of laminates of metal skins and paper are described. The truck walls provide good structural characteristics while still minimizing weight and cost.
In one aspect a structural laminate is provided having first and second skins of sheet metal. Each of the sheet metal skins has a thickness of at least about 0.005 inches. A fibrous core layer is provided between the sheet metal skins and is bonded to the skins. In one aspect, the fibrous core layer is impregnated with an adhesive resin which bonds the core layer directly to the skins. In another aspect layers of adhesive are placed between the core material and the skins which bonds the core to the skins. The resulting laminate structure is extremely lightweight compared to a single steel sheet of comparable thickness and strength.
In one aspect, the fibrous core is paper and the metal skins are galvanized steel to provide corrosion resistance.
In still another aspect, the fibrous core layer has a plurality of channels extending between the metal skins. These transverse channels are filled with adhesive to create adhesive bridges that further bond the skins to the core.
In still another aspect of the invention, a method of forming a structural laminate is provided. The method includes the steps of placing a fibrous core material between two metal skins and applying pressure to the trilaminate to promote bonding between the core and the metal skins. In one aspect a number of trilaminates are prepared which are then stacked one upon another and are then pressed to simultaneously bond the individual layers.
In still another aspect, the present invention provides non-planar laminates and a method of making non-planar laminates. The method includes the steps of forming a laminate by placing a fibrous core between the metal skins, providing a means for bonding the core to the skins and forming the laminate into a non-planar object using metal forming techniques. In one aspect the metal forming technique utilized is a die press. In one aspect, heat is applied to the laminate either before, after or during the die press operation.